Investigation of Inflammation in Alzheimer's Disease and Related Dementias (ADRD) Using [11C]-CS1P1

The primary objective of this IND study is to further evaluate the \[11C\]-CS1P1 for PET imaging of S1P1 expression in healthy older adults and in adults with Alzheimer's disease and Related Dementia (ADRD). Investigators will complete imaging of the brain and neck in older adults with normal cognition and those with clinically diagnosed cognitive impairment from ADRD to characterize \[11C\]-CS1P1 uptake in the brain. Investigators will compare the normal cognition participants to patients with ADRD to collect preliminary data that will subsequently test the hypothesis that \[11C\]-CS1P1 uptake is elevated in patients with ADRD.